1. Field of the Invention
This invention relates to a toggle press.
The concept of the press according to the invention resulted from two happenings some years ago, the first being the inordinately high accident and injury figures in respect of press operatives, attributed to the use of bar operated flypresses, foot operated assembly presses, as well as hand operated mechanical toggle presses (all of which are notoriously difficult to interlock guard and yet to be easily accessible when opened); and the second being the subsequently declared resolve to replace these types of machines with some form of power operated bench press, capable of more efficient guarding with interlocks, and to satisfy the Health & Safety at Work Act 1974, yet still be capable of accepting the huge inventory of existing press tools throughout the country.
Although the term `power operated` was not specifically defined for design purposes, it was clear that the options available were diverse, i.e. electromechanical (flywheel, clutch), electro-magnetic, hydraulic, hydro-pneumatic and, finally, purely pneumatic.
The last named power source seemed to be eminently preferred, chiefly from the safety aspect, but also from the great flexibility which the medium of compressed air, together with modern control valves, afford to a basic simplistic design.
With all the above in mind, this new press design may draw upon all the latest developments in materials and machine elements, so as to enable one basic design of press frame and pressure mechanism module to be capable of an infinitely variable number of specification permutations as to meet almost any potential user's needs without recourse to the design of a special purpose press `per se`.
2. Prior Art
It is known to provide a toggle press in which an air ram is employed to straighten a toggle linkage and thereby lower a press tool. In practice, it is arranged for the toggle mechanism to pass slightly beyond the fully straight position but even so if the tool is held in its lowered condition, the pressure will decay.